Given the mandatory reliability for telephony devices providing the infrastructure for the public switched telephony network (PSTN) and packet-switched networks, many telephony devices for interfaces, switching, and routing data or calls require a backup in case of failures or maintenance affecting operation. As such, many telephony functions require redundant devices wherein one device is active when the other device is inactive. When the active device fails or requires maintenance, the inactive device becomes active and provides the functionality for the now inactive device.
Traditionally, signaling and control messages are communicated between the redundant devices and with other devices in the telephony network using proprietary protocols over direct, physical connections. Unfortunately, these proprietary protocols and physical connections limit upgradability and the manner in which these devices interact with one another. Product and system evolution is hindered by the existing infrastructure and protocols.
Given the extensive use of the Internet Protocol (IP), and its uniform and network-independent addressing, providing communications between telephony devices for messaging and signaling is preferable. However, a major hurdle in the conversion to IP-based communications is the difficulty in maintaining IP addresses for the redundant devices used to form a telephony node. For example, when two redundant devices are used to form primary and backup devices for a given telephony node, only one device will be active at a given time.
The active device must appear to the rest of the network as the node and be associated with a single IP address for that node. When the primary device fails, the backup device must take control and appear to the network as the node with that node's IP address. This requires the active device, regardless of which device is active, to appear as the node and communicate using a single IP address when active. Although the rest of the network needs to communicate with the node, it is often necessary to communicate with both devices within the node for status inquiries and maintenance, regardless of activity.
As such, there is a need for an efficient and reliable way to provide IP addressing in a manner allowing redundant devices to communicate using a single IP address independent of the active device. There is a further need to maintain the ability to communicate with these devices regardless of their activity.